Creating files with reserved Windows file names creates issues within Windows

• Your Windows build number: Microsoft Windows [Version 10.0.15063]

• What you're doing and what's happening:
  echo "foobar" > con.out

This creates the file con.out in the current directory. It is totally usable from bash.

But from DOS, you cannot look at the file, rename the file, or do anything with it, because "CON" is a reserved file name. You cannot even rename the file from Windows Explorer.

• What's wrong / what should be happening instead:
  Maybe a warning should be issued if from Linux, you are creating a file that has a name that is invalid for Windows. Or it should not be possible to create files with the reserved names.

Apparently, these are the reserved file names:

CON, PRN, AUX, NUL, COM1, COM2, COM3, COM4, COM5, COM6, COM7, COM8, COM9, LPT1, LPT2, LPT3, LPT4, LPT5, LPT6, LPT7, LPT8, and LPT9 (see https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx)

Reproduce echo "foobar" > con.out on the reported Windows build and inspect how WSL handles file creation and Windows-reserved names. The issue does not name files or tests, and its proposed outcomes differ; completion would require an agreed policy that either warns about or prevents names such as CON, PRN, and AUX.